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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb6bc69b8fd360670726775059fb4093f3d1a7ffe76d3f8c8d9c0b7d218d2c67' 
  AND token = 'lRtKlYeaZOAB639ZjFVpHH0dRfw/xSuiy09eMrn5UTw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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