SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50a01c249aa1e5371a96872f713134aa1abdeea0002d999c347a6ae53d3dca4a' 
  AND token = 'BPDhxDNvo8PSbHH3BYBF8v9JL2iZ2KDEHKMgQQ2jNg4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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