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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21f82d5f4e8c2bebcc05af03c5a2d0daeb1ea54e640c29e051d2b71dd3a8f5e2' 
  AND token = 'PlH+AJF1z8/TMlVEO/1jQLOuWwxNA8r6zufjcLH1DCc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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