SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '27b9c8fe054d4e8f023fbca3dafdd4d83077cc9690c12d1a67c8268821336113' 
  AND token = 'DMZhvfItCUcgaXytYVo5UwHFRDvlv522zcBbXLOJaJI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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