SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b345ecb2c8ce22be5f89e582118a3f46235043bf6fa8cea387518ee442623fae' 
  AND token = 'lpClGABS9nk/SC2TsF766sNXB/QaEodkKlelCQ0ztjY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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