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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fe940f05997c5351498bc69cc054db5da7f0563e6d89f6bb21a4d6ab6902336' 
  AND token = '21CCsaqDflcSxM9C5o021b07PAFSgcrVJw2cPJiN/30=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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