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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6e3f9273ea5eaa5e3e0cd93a9e35f13c19592be8dd2cb1dae56df3f6e5c4928' 
  AND token = 'gj4hS9vcNKwohmDCsnjhTPDFzMSw4GNAyx5JjDNPPSk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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