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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1ab94db98d34c21eca7fda32a2feaeaf515d09e99f98f326c10e12ebc05188d' 
  AND token = 'BQmQmg1fs/CNZGbcfcZ79kfMLEY+fiuq8KPQ/v7Xaq0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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