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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '45adc929ee6e763f702160af895889e8a5829451a920bdc90f0452640e5c319b' 
  AND token = '21m7rhe5MyvtMk7giZOC+5fYw9z8lUQT4UrVMiZi9kg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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