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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53d8ea1ef3c4404c033a70a2ba51ccdadbf10a9dc324fd64b820de0398b966b2' 
  AND token = 'SmCEE1zYxiO4CseTaVzrfHbL0uZpqFkFga2zV/toTSs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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