SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a93c0d9c04b90b08985515fc8737742fc7a56f06950d87dac1538938bdb659' 
  AND token = 'J6RL9y0UbXpOpQ3PYGYv1qaGZAbXudm0zKjJ1YACUws=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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