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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef50490f8e2f08da1bc3c0966d0d23b39055def1d5cddf34ab90a945d661e3ef' 
  AND token = '+FvWH/AGN6YcB9tosoRYYPf5CF0PpCdmg2DvidtrQes=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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