SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71c67522be2ae9cd3e07f00ae7c5069a103824ddbc14953552641994cbc6f290' 
  AND token = 'MmxdGULT/gJSa3UpgGjAXplk38eg+K5f5ZKUHB7Jr/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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