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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8e44455721e2d5fd0cce5ca73868cf06e41f9dc7d0bb2ab375391d7af4c0763a' 
  AND token = 'U+Ar5AKc9HSfdvEv7NQVYrNWza0y4rYCY/KznGWJokI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}