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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8dfaeb2670ebe1159f5e0d24706b88341d7b877b6029297a0ca9c3d6af4456c' 
  AND token = 'N9tlaF0MhDCsgBbczNVXaZEs3sQ/Z8xyY5Zmo9gc0G4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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