SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1f251a6b713ad783ba47f3256bb074bcab46c17cdee978e20079033d3a026cef' 
  AND token = 'QLeUbwEtOgqEv+d4Bh/GtXmRv4gbtOBqfYjy5FFQJF8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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