SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f2e367f3773286e7b46ba537c53908efdd9e802aaa82efdfb98def22d84a9419' 
  AND token = '/hDnSSEy2KZbqmDCerXhxYxMxuxDaZycoPHMHt2JFCA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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