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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8fb935abcb1f43d98cea776d824d2d850c7090e854779102ce62db8a3a4849c5' 
  AND token = '34mzfwDcfPWLAsJZmRSmwAlEr4nmtCYasePmtEE7CEQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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