SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6dcbdd8fe102a385e50f3b317511f02059d9355070268b90ce0c5a547d0a5442' 
  AND token = 'o2eR9OtvxNYdgZ30YkyBzf1Fg9jSngocYNISge/Nn+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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