SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '44abe3ea99deeebb60e0553070afd3a84d874cd96f9500358ede31197b8dbdf1' 
  AND token = 'z9JaYkJGGxkO6TKYRpJ/KD8YQCMJRcsLoxRqudWr2Xg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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