SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '741dc9278c4b5bf1c503548709e8e51339e58d0202c7acca411922a3be003e5b' 
  AND token = 'iY5lPHrGwmSegLgMGUZFju5JtdA7aNpnSpLE/ZBRHEw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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