SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '512d6d2427919bd1355e1a076985fbdcd58598954bc6d244c774aa6dbadd8571' 
  AND token = 'DPje7zuRo8c5O8Kw2XAnYZOzQChSTGntDFBxSn1WzTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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