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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c21442cfc4226f529cd683aa7ef3aeee82f2ffd8d7e1286c7bcdd12f3226124' 
  AND token = 'x5xDOTobU+WSyJ4LGP4Y6ZR32Wayv3r4NvTTqisRBFQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}