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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dfd120fb348625b0aad1f2d6826ec42b3b0c401fb78c1eccc604d373f16cf3d1' 
  AND token = 'lL3bmeFSwrJVzcR0CVigBXCw0CHIlqFGGRMRwhe4Pf8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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