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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31b1e25a2be2081ffda480403207600427e5e824bcd49ca82760a4e4c1bf1cff' 
  AND token = 'D5eehKP8QLItY6x3hQSGPeLPJHpQvN//279hCYP5YdM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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