SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50d55979590f1ff207d4d4190f434aac6a7ff306896be2303dc58fc802c68742' 
  AND token = 'PEYrVbPlcsc58LUTEfVxWMekIzql5eakWrub1Uat0AA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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