SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6b8d38c8a666681f84e41d52e0be526b511157c88a1ba532894372b581bdadb' 
  AND token = 'UWyDxowzFuaOdaeusUHeh1I20I1JnfRuwNMA7lhwofk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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