SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a5b849396b8db3e941568a478b6747630b9187873c2155b7e65300fd274775ba' 
  AND token = 'JZ1IiYpRvbplRoAK3EHCm8M9xVzCN3Qu6wLCLmaq19Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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