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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21f71b52c62db41ed87378daabd1be80cc820722afd18a9ce67250b75e884358' 
  AND token = 'czrbSE+2JAUjtUWv2MkG83sVvCWFlkciXC9DAbtkOfA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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