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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fe5e0ff5ac0e5a971fac956417de1ae839c50e8df309ab603498e5f906f18a8' 
  AND token = '4ud+DXhCRNT4Rk87bVel5LcJxGjovopdGEqmcWuASI8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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