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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '506a9fcf177a4740fefffc7d7073a3c958e27d65e7319fb9022d531be5ad1c52' 
  AND token = 'oJNoexknt2RS3ktYrKrO5oPzdgVC7OGQR8lFgiQgLzI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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