SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9a5b55fa573b846bbe6a8861d08d35925db042b19c3dd05bde8ce145565f31d' 
  AND token = 'sLXgbdtDQkdZjdxU8aPtU2W7kyGdADt5FvmBE/xi/nY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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