SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a75d4797bc2d5b5f7c8623859d6c28bbe67c9ac10729fd618e7d54afff69933' 
  AND token = '6Zh8jxxJcNPyNz0Wb4NeAGdCpjrz1RuvEOIgqO8BGzc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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