SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '781dcdf6361546edc44b049ab4e1b26ef517032a947c766f178eb464bfbeff0f' 
  AND token = 'w352iH8FsK8d3AFol9VUkGXs/CwRugH4VQJPQBWBa2w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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