SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a656876683146825deecafeddf13093f1d8e8e03d25a5641a54df3abbe33c1d2' 
  AND token = '3WtoO2mH2ueiGDDbpz4MTE1Q+rzR/Qq2eT+F0pp2Tuk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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