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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '237cffc3df174d4ecc07074a0add9c451693005d9834da18b30e00a60a41bd36' 
  AND token = '8crmtJcWjgbop7ytBPlGRuj1O1hQfDpxAD30Bkj+7vM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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