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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fd41e6eccf1b37a965402027ea30311ec4e9340cd47b2b0df84eb8a96400ebc5' 
  AND token = '6x48ePmAHauHL5+qDGnceN/AxgNGOU39y2uVCMTunR4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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