SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a2840c266f01dbd9f242f8029f87175802605ea70e93bc23e94bf9afd7678a2' 
  AND token = '56UnASCZLixPiwBVfcWnv5dZUPYSFG3t9TCdVovK0DU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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