SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '268a29438d99b88e4f1bbabbfcbc704d23f054cda75fd73e9182fe7c57e25677' 
  AND token = 'JoVVvYmMDqofV8K5YjATxjlElTq89/1jVBSefInum0w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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