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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3b21738d7f73142788f92f8d6c0521af67afa71d63ec321dbfe766ca8bc51da' 
  AND token = 'sWLaMCPsJfw7aupPhs6jhF9nKocjeWsFVC0agtcqP+U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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