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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '546bf0fda7358f41c77fd8432cb8d3527fdd7149b4d74dd8a4f6d6e2341a8728' 
  AND token = 'tEWocpQQuE0tfJtB2bnWY14FhnnQtbyoWIeW8Avgsys=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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