SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df6c5fe88d16977389878ae323a9233937357abdebb2985eb66891644f560d7c' 
  AND token = 'UTrZSma91eenIHThdKZNN583IBezkyaK8Mldwy0nlPY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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