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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a42b18d93f679064d40b945b1c84dde82e8a097b23f736bb859d0c31ae7ea1a2' 
  AND token = 'QF4iRN8dfpYGKihiWxaXJ+cyQyKDAGIvAqrjsSRdxpc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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