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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '517823b90235ddf6914a75f4cf077f123d6a7bd501e1d7c9a22da6bd12c75c07' 
  AND token = 'UNGegiSvWI7pMeIFEydaL7j0zQ3MyjEvGINzQA/puEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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