SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53f6dbbecc851f73cf842467cd7fac2d5ac604b714bd45f1b24fc9d002f81b76' 
  AND token = 'UAai6TqrCzlghMEALgzTB6SiJhg/ANCMnPHFXKp4EZk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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