SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21d1a6c7df8472a8c8369393d1e6c0bd2a05dfa47872b862e3af563afa47baaa' 
  AND token = 'nYIYGcpAQqoNVRMSbGLGmO943QrGaWMsUhtaqJ3nVFs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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