SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e78675cfdc04d82f423c132bb921b77ecb19bb7d758369e8c221ee7268b5c62a' 
  AND token = 'meJKkBMsL+2HArb9vI00DJ5nruCPOljkyQMizY6UdEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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