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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '335667b42b3860f0d8bbec80ad9368339ece51b1d5cc7e10974a4680722aa39f' 
  AND token = 'fvThp+UmK/HM83lHkysZ/baZa1RdA4dQiefq2siStvo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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