SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4eddb02a14af55dc679390259a45f78104e664076b3be539aa9d3b3838294a14' 
  AND token = 'yuqRQcc/HBSrIBZ+yzRMOAiHZmfK1PfQTjj80NIgi38=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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