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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a23752dc3b4df46daeceeb9546a628ff21cf200ee44855b591ef0134c3ed4282' 
  AND token = '9xAM3BOR2erxb91IsDpxgtD6VJH4fUEOgDkK7d+jvnk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}