SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '308feb21f964e6b6454e42aebafa2b2a2d02afdb474d412246e412f8a34d4a44' 
  AND token = '3daQfYsdot91QbjCYWaLB1+JvRgbw59IauR0zSQDJoc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00059

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}