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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2cf2a9eeea9758cce0fdcd3ae683f4e09fa6802c0c6bf33d61fe26da501a2456' 
  AND token = 'PkmY/JfhrBnE1B8CNu/MhG3zfKTaqXdcJqUDSBL1Xjs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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