SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0409913912293393bcf17a582b9d1af4f341c12bd959527f38aa4603d23dfc2c' 
  AND token = 'rslmtleNsDLdnevvweP84Tj+pyQ7euRmpP0zdCRIJNI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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