SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8831c92d41a38bb683742ebe7383ab767ff305f00df3182228d8cb039af8a83' 
  AND token = 'JhjNa75ndzRuQIwe60LjxZ/RBIHhjeUgA0D9e+QukMM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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