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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '821df60147d604ae2a49105823099d500bdbdf7e212fb1dd7e08dcfdd707bf20' 
  AND token = 'G+WhDS9fVkoVbdBw6j99VC7fKDFHHEaGTp6FHNeqabU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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