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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a5c1c292aeccd6723621ee9a1fa3a83e142ae09481d5d1d3d6185bcfe05b7563' 
  AND token = 'a1QXIZFIFCFGMYlyiUAPOBzLAVBO+bzuhDm3w/FzecU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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