SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '210d0ce53a7af0adda78c407fde0db622627030ca038fbd2988e099f36756446' 
  AND token = '5AvyMaVlT3xfUZWiBYys+VxzBDIWWn0PtmxqwzZBnjE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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