SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '259c44e5ec2313cf957b31c393fea66774cfd57af79060bfe7553c4ca02b1a44' 
  AND token = 'O/BwgZIMdlpcp7mpJKf3Jdy0zBujVmKd5hgMAUAz18A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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