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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b50491d996d0ed12d7b64a6e27f9b7e47e518d7f324c1631c439f7c0119a989b' 
  AND token = 'rCff1o/icEpBrb5RjOjxpXcmsj7DpDaEmw8y8zTTEXw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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