SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6b37ca78339cc15ec31f85aef85a53b11676c5cb117586de617204f39769f55' 
  AND token = 'gkLRhY8zOftBIjYN/+dmSpG7CcqMV6jqb040+FXk020=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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