SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fe0f07678a012127e7acdca3e62424957e9b7d8cb4da81c5a4e4f3031c6685c' 
  AND token = 'pSM+4ddIueCx3mHcCo48UixsvDmWc5vqx7wuvy47IAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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