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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21ce81de70154c9637fb365a7bc9d8542b16e6e71ec9fd66a83329855a98c047' 
  AND token = 'kLhgBiy7TQRT6/lJdmwUMn/s4XpXiNPkvAXn4vnQw9Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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