SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a392755bed284225094eb95b3f5ce23430b6827d076776ad0b71952cce775158' 
  AND token = 'W46OD1OCnAUJIu158JnBJZI8/gkZvyRALMMil4km74k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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