SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6737187602f2d50d6be69b6d392350819572fb034dcc1a8813c13b14ce47fc6' 
  AND token = 'UK8bxPp8GoLqkvr222uNehEsUuz4I3Zu5hp8olBMgOA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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