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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a40d14ec7ccf8f842b2a632d81fced63dfe4692696b28ed3afc0231d790c1f9' 
  AND token = '4/7GQQuDYBeSk78KCfgjjOYrVb0TkL+Pff2n3SNQ0ks=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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