SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6738b38b6c0da5470451c286ea2361874301f5a9a0431780be8ff9bd78490574' 
  AND token = 'rZJR0VowhNGUuLPJq8r9714MT1lDJ2VWvvuTZozd194=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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