SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df90519fed1fa84212d4232352b815945149e0c7cf4fc804005f7952fb79e506' 
  AND token = 'VVIUON/BHKcCzctCZBN8aE5vcaEOW6eMKpAbFtZOabA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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