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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8278a6f367fba1e2269b524a53efcd963d261470bfde3e43c2d6f8bd793c9ec4' 
  AND token = '3O4vYhfFAE1qfGvoWqCqSVIxCV7hc7uuXXA7LoYTwgE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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