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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f3a57c67a6017f0df538f44754121ef69a373009c47f5d823402435a344c94e' 
  AND token = 'oPDtyCWZz5btt9cTK1BvXMshZAyddHO//o6+HvOLhk4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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