SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6503ad55c594dc2a0b7ba1b917869134604c275ae87162ba56628a00e20450f3' 
  AND token = 'inRFEMvGNSJoRVZ4GgSUZXSRfSNMnOlVdrJ80NejIEM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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