SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3ac65ffc07c805c561d0bf2f4f57aa71883643803b1473cb57d5133582086b6' 
  AND token = 'r8TnRFXiaxXb5IRoBXFvF8CUXxordxglY5uuApCZglc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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