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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b138c1ab7e4d91e41fa04d7cb2dd61828cf2a53c0c06af2258b7f367a124a964' 
  AND token = '4ErOZm7hC8ymj07OWX1Wk0h40hltjhCGE4QAPLv0ZNM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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