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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3068f816835276c0bc35dc949c94b7dd0937a5dd31d37b0d4ed123f1b8cbf21' 
  AND token = '1nfNk7Pck8gRsGRO6uqHWHw62VEBcyLScjq+OphFUsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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