SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '821e517525968186207cf59f5c8018c1caff32ac5d8a0e065d8a3a91ee0113b9' 
  AND token = 'gSqSjzwypVNsWHU3IYM1juGTCMHS36nf4k+nbooOEhE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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