SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3773313340c3cc86bc11de4e8025101da2b5138a41ff58f95e3e17ce7169a6f8' 
  AND token = '5/KU0iwrvFGy7mENOFycNwiznkldUVsuBpewUXbokWc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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