SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '925707f8f863beb9092e0f25e1bebeb28175139363918b07c9f9011ed9340981' 
  AND token = '9zfUWh8qzTPDYUy9ISFssGTwLmXfoVXPygKZBKBRg4w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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